Britain's Supreme Court, the country's highest judicial body, said on Friday it had granted permission for WikiLeaks founder Julian Assange to appeal against extradition to Sweden over alleged sex crimes.

Swedish authorities want to question the 40-year-old Australian, whose website's activities have infuriated the United States, over accusations of rape and sexual assault made by two female former WikiLeaks volunteers in August 2010.

Assange, who has been living in Britain since he was detained on a European arrest warrant in December last year, denies wrongdoing and has been fighting a legal battle to avoid being sent back to Sweden.

In November, London's High Court upheld the extradition request but earlier this month granted him the right to apply to the top court, which has now agreed to hear his case.

Britain's Supreme Court said his two-day appeal hearing would start on February 1.

The court has decided that seven justices will hear the appeal given the great public importance of the issue raised, which is whether a prosecutor is a judicial authority, it said in a statement.

Assange argues that the European arrest warrant is invalid because it was issued by a prosecutor and not a court or a judge.

He has also previously argued that the case against him was politically motivated.

In 2010, shortly before his arrest, WikiLeaks posted 391,832 secret documents on the Iraq war and 77,000 classified Pentagon documents on the Afghan conflict.

It has also made available about 250,000 individual cables -- the daily traffic between the State Department and more than 270 American diplomatic outposts around the world.

Bradley Manning, a U.S. army intelligence analyst suspected of leaking the classified documents to WikiLeaks, is due to make his first court appearance on Friday over his alleged role.

(Editing by Tim Castle)